An injector provided to an internal combustion engine is an electromagnetic valve switched between open and close states by moving a valve body inside a cylinder. When a voltage is applied to the injector and a drive current flows to a coil, the valve body moves due to an electromagnetic force. The injector is thus switched to an open state and fuel is injected to the internal combustion engine.
To inject fuel supplied from the injector in a quantity coinciding with a target value (required injection quantity), it is necessary to appropriately control a time-variation in drive current flowing to the injector, that is, a current profile. However, the current profile may vary with, for example, a variance in electrical resistance across the coil of the injector or in magnitude of an applied voltage. When the current profile varies, a behavior of the valve body of the injector varies, too. An actual injection quantity thus deviates from the target value.
In particular, when the target value of an injection quantity is small, a variance in current profile gives a considerable influence. A variance in current profile as above may possibly occur due to a difference from injector to injector and a temperature change of the injector. A variance in current profile may also occur due to deterioration of the injector.
Patent Literature 1 specified below describes a control apparatus capable of limiting a deviation of an injection quantity caused by a variance in current profile by correcting a voltage application duration to the injector or a target value (maximum value) of a drive current.